1. The Field of the Invention
The present invention generally relates to optical signal switching devices. More particularly, the present invention relates to an optical switch that enables both signal transmission switching and reflection in a single device.
2. The Related Technology
The increased demand for data communication and the remarkable growth of the internet have resulted in increased demand for communication capability within metropolitan areas. There has also been an equally large increase in demand for communication capability between large metropolitan areas. Optical communication systems using a network of fiber optic cables are being developed and installed to meet this increased demand.
Various types of optical switches for switching and routing optical signals are currently used in communication systems and computer systems. For example, one type of presently available optical switch includes a matrix of thermooptic switching elements interconnected by waveguides formed on a silica substrate. Switching of light signals is accomplished by the use of thin film heaters to vary the temperature of the switching elements. Electrical circuits are also provided to supply switching current to the heaters. A heat sink may be provided to dissipate heat caused by the switching operations. One example of such a switch is shown in U.S. Pat. No. 5,653,008.
Other types of switches, known as planar optical switches, are currently available for some applications. Planar switches are often fabricated by Ti-diffusion in LiNbO3. Switched directional couplers represent one example of LiNbO3-based switches that are commercially available. LiNbO3 planar switches are characterized by high switching speeds, often in the sub-nanosecond range. However, such switches are generally sensitive to the polarization of the light forming the optical signal, which can limit their utility. Furthermore, LiNbO3 switches are relatively expensive to manufacture.
Still other optical switches use a semiconductor substrate with vertical current flow to heat active regions of the switch and enable routing of the optical signal to occur. One example of such a switch is shown in U.S. Pat. No. 5,173,956. However, such optical switch designs often have poor scalability, relatively high manufacturing costs and low optical signal bandwidth.
In addition to the above, some optical switching applications require selective reflection of the optical signal, in addition to traditional signal switching and routing. One such application where this is desired involves the reflection of optical signals between primary and secondary optical transmitters in a redundant optical signal communications system. Though devices to reflect an optical signal are present in the art, optical switches that provide both switchable signal transmission and signal reflection are not.
In light of the above, a need exists for an optical switching device that overcomes the problems present in the art. Specifically, a need exists for a unitary, low-cost optical switch capable of both wide band optical signal transmission and reflection. Moreover, such an optical switch should be readily integrated into a variety of optical systems, such as fiber optic communications systems.